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Unformatted text preview: 1 ECE331 Excess Carriers in Semiconductors Lu ECE331 Carrier Generation and Recombination GENERATION : The process whereby electrons and holes are created. ( through some excitation ) RECOMBINATION : The process whereby electrons and holes are annihilated. ( by emitting photons or phonons ) Lu Excitation (Thermal, Optical, Field, Bombardment) 2 ECE331 Band-to-Band Recombination and Generation (Direct) The simplest process is BAND-TO-BAND recombination in which a free electron in the conduction band drops to fill a hole state in the valence band In the OPPOSITE process an electron-hole pair is GENERATED when an electron is excited from the valence band to the conduction band E c E c Lu RECOMBINATION E v PHOTON GENERATION E v PHOTON HEAT ECE331 Indirect Recombination and Generation ANOTHER important source of recombination and generation in semiconductors is the existence of so- called R-G (recombination-generation) CENTERS * These are IMPURITY LEVELS associated with lattice defects or special impurity atoms which give...
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- Spring '09